The invasive species, the Bullfrog is also known as Rana Catesbeiana. Bullfrogs are usually green to greenish-brown. If they are from the South, they are usually spotted. They have a broad flat head and body. They grow on average to be about 3 and a half to 6 inches and weigh about 750 grams. (1) Detailed Descriptions Bullfrogs get together at breeding ponds in early summer. Males search for territories and safe area for egg-laying and places to defend them. Males compete by calling loudly (mostly through their ears (3)) to attract females. After mating, females lay up to 20,000 eggs in a film on the water’s surface. Depending on the temperature, the eggs take four to five days to hatch (2). They take about two years to metamorphosis from tadpoles into frogs. Bullfrogs pretty much eat anything they can fit in their mouths. Bullfrogs are highly predatory, consuming insects and other small invertebrates, birds, small mammals, snakes, and other frogs (including smaller Bullfrogs). They even eat ducks. (2) Their aggressiveness and ability to eat pretty much anything they find in a pond, it is easy for them to dominate (1).
Habitat and Distribution Bullfrogs are native to the eastern United States, ranging from as far north as Nova Scotia, all the way down to central Florida. They also have spread as far west as Wisconsin and the Rockies and were introduced widely throughout Colorado, British Columbia, California, and other western states. They live in vegetation along the edge of large, slow moving, bodies of freshwater. Their populations can bloom out of control because they don't really have natural predators.(2) Impacts Bullfrogs have their positives and negatives. They are good because they eat pesky insects, such as mosquitoes. They are bad because they have no natural predators which are not a good thing because it means they dominate wherever they go. Adult Bullfrogs hibernate at the bottom of breeding ponds through the winter. Bullfrogs come out of hibernation in the spring. (2) Bullfrogs do not have too big of an impact directly on humans. They eat mosquitoes, which is a positive because that reduces the risk of the West Nile Virus. They they can give off some nasty toxic secretions from their poison glands (called paratoid glands) that can poison a dog if it tries to eat one. (1) The bullfrogs do not have a huge impact on the economy, unless they get into gardens. (4)
History Its natural range is in the eastern part of North America, from Canada as far south as Florida (1). According to biologists, bullfrogs began their leap around the world in 1898, when they were imported to California.(5) It was introduced to other countries in the early part of the twentieth century by people wanting to “farm” it for its meaty legs. It has spread through much of the Lower Mainland and southern Vancouver Island, and has also been found in the South Okanagan. It is widely distributed in the western United States, where several introductions also took place. (2)
Control Measures
There have multiple attempts in hopes of controlling the bullfrog’s population. Rotenone and other toxic chemicals can be put into ponds to frog tadpoles, but grown bullfrogs can just hop out of the water. Researchers have had some success controlling bullfrogs at Buenos Aires National Wildlife Refuge. They have drained bullfrog-infested ponds during the dry season, killing bullfrog tadpoles. Scientists are still looking for more effective ways to keep up with the female bullfrog’s ability to produce 2,000 eggs.(5)
Christina Savage
General Information
The invasive species, the Bullfrog is also known as Rana Catesbeiana. Bullfrogs are usually green to greenish-brown. If they are from the South, they are usually spotted. They have a broad flat head and body. They grow on average to be about 3 and a half to 6 inches and weigh about 750 grams. (1)
Detailed Descriptions
Bullfrogs get together at breeding ponds in early summer. Males search for territories and safe area for egg-laying and places to defend them. Males compete by calling loudly (mostly through their ears (3)) to attract females. After mating, females lay up to 20,000 eggs in a film on the water’s surface. Depending on the temperature, the eggs take four to five days to hatch (2). They take about two years to metamorphosis from tadpoles into frogs. Bullfrogs pretty much eat anything they can fit in their mouths. Bullfrogs are highly predatory, consuming insects and other small invertebrates, birds, small mammals, snakes, and other frogs (including smaller Bullfrogs). They even eat ducks. (2) Their aggressiveness and ability to eat pretty much anything they find in a pond, it is easy for them to dominate (1).
Habitat and Distribution
Bullfrogs are native to the eastern United States, ranging from as far north as Nova Scotia, all the way down to central Florida. They also have spread as far west as Wisconsin and the Rockies and were introduced widely throughout Colorado, British Columbia, California, and other western states. They live in vegetation along the edge of large, slow moving, bodies of freshwater. Their populations can bloom out of control because they don't really have natural predators.(2)
Impacts
Bullfrogs have their positives and negatives. They are good because they eat pesky insects, such as mosquitoes. They are bad because they have no natural predators which are not a good thing because it means they dominate wherever they go. Adult Bullfrogs hibernate at the bottom of breeding ponds through the winter. Bullfrogs come out of hibernation in the spring. (2) Bullfrogs do not have too big of an impact directly on humans. They eat mosquitoes, which is a positive because that reduces the risk of the West Nile Virus. They they can give off some nasty toxic secretions from their poison glands (called paratoid glands) that can poison a dog if it tries to eat one. (1) The bullfrogs do not have a huge impact on the economy, unless they get into gardens. (4)
History
Its natural range is in the eastern part of North America, from Canada as far south as Florida (1). According to biologists, bullfrogs began their leap around the world in 1898, when they were imported to California.(5) It was introduced to other countries in the early part of the twentieth century by people wanting to “farm” it for its meaty legs. It has spread through much of the Lower Mainland and southern Vancouver Island, and has also been found in the South Okanagan. It is widely distributed in the western United States, where several introductions also took place. (2)
Control Measures
There have multiple attempts in hopes of controlling the bullfrog’s population. Rotenone and other toxic chemicals can be put into ponds to frog tadpoles, but grown bullfrogs can just hop out of the water. Researchers have had some success controlling bullfrogs at Buenos Aires National Wildlife Refuge. They have drained bullfrog-infested ponds during the dry season, killing bullfrog tadpoles. Scientists are still looking for more effective ways to keep up with the female bullfrog’s ability to produce 2,000 eggs.(5)
Jeremiah Was A Bullfrog
How Bullfrogs EatJabba Eats Mouse
Works Cited
"Bullfrog." All About Frogs. 12 Nov. 2008 <http://allaboutfrogs.org/info/species/bullfrog.html>.(1)
"Bullfrog." B.C. Frogwatch Program. 12 Nov. 2008 < http://www.env.gov.bc.ca/wld/frogwatch/whoswho/factshts/bullfrog.htm >. (2)
Milius, Susan. "Frogs that talk through their ears. (research indicates North American bullfrog uses its ears to amplify its croak)(Brief Article)." Science News. v153. n1 (Jan 3, 1998): p12(1). Student Resource Center - Gold. Gale. Stroudsburg High School. 13 Nov. 2008 <http://find.galegroup.com/srcx/infomark.do?&contentSet=IAC-Documents&type=retrieve&tabID=T003&prodId=SRC-1&docId=A20302248&source=gale&srcprod=SRCG&userGroupName=stro53037&version=1.0>. (3)
Environmental News Network staff, comp. "Bullfrogs' serenade signals trouble in Canada." CNN Aug. 2000.(4)
Roach, John. "Invading Bullfrogs Appear Nearly Unstoppable." National Geographic News 28 Sept. 2004.(5)